1. Field of the Invention
The present invention relates to a relay connection management program and relay connection management method. More particularly, the present invention relates to a relay connection management program and relay connection management method which can easily implement TCP/IP relay connection management without burdening a relay system which employs a high quality transmission path such as an internal bus connection, for example.
2. Description of the Related Art
FIG. 11A shows an example of a relay system. As shown in FIG. 11A, when implementing a relay system which relays communications with end systems 92X and 29Y according to TCP (Transmission Control Protocol), a relay system 91 terminates with the end system (end node) 92X at a TCP connection a as well as with the end system (end node) 92Y at a TCP connection b.
Such a relay connection normally has protocol stacks such as those shown in FIG. 11B. The relay system 91 is equipped with a sort of symmetrical protocol stack of both end systems for relaying connections. Therefore, the relay system 91 must retain connection information for each of the end systems 92X and 92Y at both ends and associate them with each other, as shown in connection management information tables 94 in FIG. 11C.
For each of the TCP connections between the end systems 92X and 92Y, the relay system 91 must enter and manage connection management information in the connection management information tables 94X and 94Y, including the remote IP address, the local IP address, the remote port number, the local port number, a sequence number, an ACK response number, re-transmission count, timer information, and information about a pointer to the corresponding connection management table.
On the other hand, to implement relay connection management easily in the relay system 91, there is no way but to relay connections at the Internet Protocol Layer (IP Layer) located one layer down, as shown by a broken line in FIG. 11B.
When relaying communications connections between the end systems 92X and 92Y, if a relay system is implemented at the IP layer for the simplicity of processes, the communications quality assurance functions provided by TCP cannot be utilized. Thus, there is demand to alleviate the processing burden on relay systems by simplifying the management processes of TCP equipped with communications quality assurance functions.
Also, in the case of TCP connection relay, the relay system 91 must manage twice as much connection management information as managed by each of the end systems 92X and 92Y. In high-capacity communications, immense memory capacity is required to store connection management information. Thus, it is important to reduce memory usage and thereby cut down costs.
In an asymmetrical relay network configuration in which a transmission path 93Y on one side has extremely high quality, it is deemed unnecessary to manage the TCP connection on the high quality transmission path on an equal basis to the connection on the transmission path 93X of ordinary quality.